1. Field of the Invention
The present invention relates to an airbag apparatus including an airbag inflatable with inflation gas so as to project from a housing area. Particularly, the invention relates to an airbag apparatus suitably used for a front passenger's seat, a driver's seat, or for pedestrian protection, further including a tether connecting the housing area and the airbag and a mechanism for exhausting the inflation gas for controlling the projecting degree of the airbag from the housing area.
2. Description of Related Art
A conventional airbag apparatus is shown in JP 2003-515483A or WO01/34436A1. This airbag apparatus includes a tether and a ventilation mechanism in addition to an airbag inflatable to project from a housing area for protecting a vehicle occupant or a pedestrian. The tether connects the housing area and the airbag so as to control the projecting degree of the airbag projecting from the housing area. The ventilation mechanism lets out the inflation gas so as to control the pressure inside the airbag.
The tether of the above airbag apparatus has two modes of operation; an increased-protrusion mode to increase the protruding degree of the airbag from the housing area and a restrained-protrusion mode to lessen the protruding degree. Specifically, the airbag apparatus includes an actuator with a movable member proximate the housing, and the tether includes, at its end area closer to the housing, an engagement portion engageable with the movable member of the actuator. On the restrained-protrusion mode, the engagement portion of the tether is anchored by the movable member of the actuator so as to shorten the length of the tether from the housing area to the joint to the airbag. On the increased-protrusion mode, alternatively, the movable member of the actuator releases the engagement portion of the tether so as to extend the length of the tether.
The ventilation mechanism of the above airbag apparatus also has two modes of operation; a low-emission mode to suppress emission of the inflation gas and a high-emission mode to increase the emission relative to the low-emission mode. Specifically, the ventilation mechanism includes a vent opening formed on the housing and a valve body. The valve body normally leaves the vent opening open and moves to close off the same upon activation of the actuator. Further, the valve body is operable in conjunction with the movable member retaining the tether.
The above airbag apparatus is designed, when a vehicle occupant is of small stature seated proximate the airbag apparatus, not to activate the actuator upon airbag deployment so the tether is set in the restrained-protrusion mode while the ventilation mechanism is set in the high-emission mode, thereby deploying the airbag with reduced volume not giving undue pressure to the occupant. If the vehicle occupant is seated at normal position, on the contrary, the airbag apparatus is designed to activate the actuator upon airbag deployment so the tether is set in the increased-protrusion mode and the ventilation mechanism is set in the low-emission mode, thereby deploying the airbag with high volume and with adequately high inner pressure.
That is, the above airbag apparatus operates to shorten the length of the tether and open the vent opening, i.e., in combination of the restrained-protrusion mode and the high-emission mode when the actuator is inactive. On the other hand, when the actuator is activated, the airbag apparatus operates to extend the length of the tether and close off the vent opening, i.e., in combination of the increased-protrusion mode and the low-emission mode.
The above airbag apparatus has only two restraint patterns of the airbag attained by a single on-off control actuator; a restraint pattern of combination of the restrained-protrusion mode and the high-emission mode or another of combination of the increased-protrusion mode and the low-emission mode.